The present invention relates generally to electrical energy storage devices and more particularly to capacitor structures having high energy storage and high power delivery capability.
Electronic equipment which is portable or transported must have a source of electrical power that has minimum weight and volume, but maximum capacity for power and energy density. The amount of energy stored and the peak power capability are principle parameters of a prime energy storage device. Compact commercial and military electronic systems have electrical and packaging constraints that are imposed by the volume and weight of the apparatus. These constraints determine the necessary energy and power density of the power source.
Examples of current prime energy storage devices include both non-rechargeable and rechargeable technologies. Nickel-cadmium (Nixe2x80x94Cd) batteries, lithium-ion (Li-ion) batteries, and ultra capacitors are all examples of rechargeable energy storage devices. Rechargeable devices are re-energized by external power sources and are optimum for multi-use applications. Ideal rechargeable systems can store charge for long periods of time (also known as xe2x80x9cshelf-lifexe2x80x9d). Lithium-based thermal batteries are an example of non-rechargeable energy storage devices. A primary energy storage device (non-rechargeable) contains an adequate amount of energy to operate through the life of the device. This type of energy storage device is discarded or destroyed at the end of use.
Existing commercial rechargeable energy storage technologies do not meet the power density and peak power requirements of future, high power electronic systems which undergo rapid mode changes during system operation (e.g., cell phone mode changes from idle to transmit). Present thermal batteries, such as used in missiles, generate enormous amounts of heat during activation and thus require insulation or remote packaging away from thermally sensitive electronics, thereby presenting additional design challenges such as thermal management.
In addition to the power requirements, existing energy storage technologies are generally packaged without considering the shape of the installation locations. For example, in missile applications electronics are generally packaged as cubic modules. Therefore, when placed into the curved interior of a missile, there are segments of the interior that don""t readily house the typical packaging geometry for current energy storage devices. Additionally, when an energy storage device is situated in an apparatus that has an internal volume other than that of presently used packaging technology, unused space remains (i.e., the arc segments that remain when a square box is placed in a cylindrical housing and volumes associated with structural features such as wings, fins and so forth). Therefore, discretely packaged battery solutions have a further drawback of underutilization of space, which can limit electronics volume and thus overall system performance.
A capacitor structure which provides very high storage capacity is described in U.S. Pat. No. 6,226,173 B1 which issued on May 1, 2001 and is entitled xe2x80x9cDirectionally-Grown Capacitor Anodes.xe2x80x9d This patent describes a dendritic sponge which is formed through chemical processing on a body of titanium. This process creates a large surface area which is then coated with a dielectric. By use of selected dopings of the anode, the subsequent dielectric formed on the anode can have a very high dielectric constant. An electrolyte is applied to the opposite side of the dielectric to serve as an electrical conductor (cathode) and to prevent breakdowns by re-oxidizing the dielectric surface at areas of local breakdown. A capacitor formed in this way can have a very high energy and power density per unit weight and volume.
Therefore, there is a need for a high energy density and high power density energy storage technology. Further, there is a need for power source technology that can utilize the currently available volumes in commercial and military applications, by, for example, forming the power source integrally with the structure and/or into unique geometric shapes.
An electrical energy source provides power for electronic equipment carried within an airborne vehicle. The vehicle has an elongate body section which encloses an interior volume. A multi-layer capacitor structure is provided on a non-planar interior surface of the body section. The capacitor structure has a conformal shape that matches to that of the interior surface of the vehicle. The capacitor structure stores electrical energy for use by the electronic equipment. Terminals are provided which connect the capacitor structure to the electronic equipment for transferring electrical power from the capacitor structure to the electronic equipment. The capacitor structure can be fabricated either directly on the mounting surface or fabricated separately and mounted to the interior surface of the vehicle.
A further embodiment of the present comprises an integrated electronic circuit together with a power supply on a planar substrate. The electronic circuit is formed as a portion of the substrate. A capacitor structure is joined to and is in parallel with the substrate. The capacitor structure stores electrical energy. The capacitor structure is positioned such that it is substantially overlapping with the electronic circuit on the opposite side of the substrate. Power terminals provide connections between the capacitor structure and the electronic circuit for transferring electrical power from the capacitor structure to the electronic circuit.
A further embodiment of the present invention is a capacitor stack for providing electrical power to electronic equipment positioned within an interior space of a vehicle. A plurality of planar capacitor structures are bonded together in parallel to form the capacitor stack. The vehicle has a shaped space therein which is at least partially defined by an exterior surface of a housing for the electronic equipment and a portion of a wall of the interior space. Each of the planar capacitor structures has a shape such that the capacitor stack in combination has an exterior configuration substantially corresponding to the shaped space and whereby the capacitor stack can be positioned within the shaped space to substantially fill the shaped space.
A further embodiment of the present invention is a power source for a portable electronic device which has a housing and electric power consuming circuitry therein. The housing of the portable electronic device has an interior surface. A film capacitor structure is joined over a majority of the area of the structure to at least a portion of the interior surface of the housing. The capacitor structure has a configuration that conforms to the shape of the interior surface. The capacitor structure can store electrical energy therein. Power terminals are provided which connect the capacitor structure to the power consuming circuitry for transferring electrical power.
A further embodiment of the present invention is a method for manufacturing a web of electrically capacitive material which comprises a sequence of processing steps conducted in one or more chambers wherein a metallic layer is applied to a surface of a film, an oxide layer is formed on the surface of the metallic layer, a metallic sponge is formed for the metallic layer, a dielectric oxide is formed on the metallic sponge, an electrolyte is applied to the surface of the dielectric oxide, and a metallic layer is formed on the electrolyte to produce a capacitor electrode, thereby producing a web of capacitive material which can be stored as a roll.
A still further embodiment of the present invention is an electrical power source for providing electrical power to equipment carried in an airborne vehicle. The vehicle has an elongate body section which enclosed an interior volume that has one or more structural braces therein. A multi-layer capacitor structure has a majority of the area thereof mounted on a surface of one of the structural braces. The capacitor structure functions to store electrical energy therein. Power terminals are provided for connecting the capacitive structure to the electronic equipment for transferring electrical power.